metamorphic
Lapis Lazuli (Low Grade)
Lazurite-rich metamorphic rock ((Na,Ca)8(AlSiO4)6(SO4,S,Cl,OH)2)
Hardness: 5-5.5 (Mohs scale), Color: Dark blue with significant black or grey inclusions, Luster: Dull to vitreous, Crystal Structure: Isometric (as lazurite), Cleavage: Imperfect, Specific Gravity: 2.38-2.45
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Dark blue with significant black or grey inclusions, Luster: Dull to vitreous, Crystal Structure: Isometric (as lazurite), Cleavage: Imperfect, Specific Gravity: 2.38-2.45
Formation & geological history
Typically forms through contact metamorphism of limestone or marble, where heat and pressure from nearby magma alter the rock. Primary source locations date back several thousand years to the Hindu Kush mountains.
Uses & applications
Historically used for pigments (ultramarine), decorative carving, and jewelry. Low-quality specimens are used for tumbling, beads, or decorative gravel.
Geological facts
Lapis lazuli was used in the funeral mask of Tutankhamun; it is not a mineral but a rock composed primarily of lazurite, calcite, and pyrite.
Field identification & locations
Identify in the field by its characteristic deep blue color and the presence of golden pyrite flecks. High concentrations of calcite (white) or matrix (grey/black) lower the grade.
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